The performance of normal behaviours is limited when horses are kept in stalls, and behavioural development may be compromised due to inadequate environmental conditions. The response of a horse to training may be affected by housing. Horses were kept on pasture or in individual stalls, and a few from each groups were subjected to a standardized training procedure, carried out by two trainers in a round pen, while the others were introduced to the round pen but not trained. For the stalled horses, total training time was significantly higher than total time for the pastured horses. The stalled group also required more time to adapt to the activities occurring from the start of training to mounting. Unwanted behaviours occurred more often in stalled horses, and pastured horses tended to have a higher basal heart rate on the first day of the study. Physiological data did not identify differences between the two housing groups. However, behavioural data suggest that pasture-kept horses adapt more easily to training than stalled horses.